On average 2,944 Canadians will be diagnosed with cancer every week, of that an average of 1,354 Canadians will die of it every week. Based on the current incidence rates, 38% of Canadian women will develop cancer during their lifetimes, and a staggering 44% of men.
One method for treating certain cancers is to use internal or interstitial radiation therapy, or seed therapy, in which a radioactive implant is placed directly into a tumor. It involves surgical insertion of radiation source (radioactive seeds) into the treatment volume through tubular needles. Tubular needles loaded with radioactive seeds are inserted into the treatment volume, after which the radioactive seeds are left in the treatment volume, either permanently or for a specified amount of time. This method is called brachytherapy. Brachytherapy is used to treat various types of cancer throughout the human body, including the prostate, breast, cervix, and lungs.
Documented brachytherapy procedure is performed manually: the surgeon inserts brachytherapy needles into the cancerous tissue by hand, pushing them through holes in a specially prepared grid template (illustrated in FIG. 1).
U.S. Pat. No. 6,398,711 by Green et al., teaches the use of such a needle grid template.
U.S. Pat. No. 6,540,656 by Fontayne et al. discusses a targeting fixture again making use of a grid template. But this fixture can only provide 2-dimensional, translatory positioning of the instrument before insertion.
Another instrument making use of the grid template is illustrated in PCT application WO98/56295 by Fanucci.
The main drawback of the manual procedure is that it is slow and not very accurate. The distance between two adjacent holes in the grid template limits achievable accuracy of needle tip placement. Further, as the holes in the grid template are long (compared with their diameter) and all parallel to each other, oblique trajectories of needle insertion are not achievable. To compensate for this, the surgeon would typically press the needle by hand from a side and/or rotate it during insertion. The surgeon does this while monitoring the actual position of the needle in a real-time image (typically collected by transrectal ultrasound imaging system) so the overall procedure is involved, requires extensive training, and takes time.
An emerging modality is the use of a robotic manipulator and a special end-effector called “needle driver” to perform the procedure (FIG. 2). In robot-based systems, the robot is used to achieve quick and precise positioning and orientation of the needle driver (together with the brachytherapy needle that it holds). Once the specified position and orientation are achieved, the needle driver pushes the needle into the cancerous tissue. To increase the accuracy of the needle tip reaching the specified point inside the treatment volume, the needle may also be rotated along its axis during the insertion. Both the axial and rotary motion of the needle are driven by the needle driver.
Robot-based systems resolve some of the problems associated with manual brachytherapy such as the coarse spacing among the holes in a grid template and they allow for oblique insertion trajectories. However, they have some drawbacks of their own:                The robot takes a lot of space, it gets into surgeon's way, and its presence and motion can be intimidating to medical personnel involved in the procedure.        Integrating the robot with the rest of the brachytherapy system (particularly the ultrasound imaging system) is difficult as the robot is physically detached from the rest of the system. The integration requires precise mounting of the robot as well as calibration of the complete system.        The robot-based system is complex and the medical team needs extensive training to learn how to use it.        Typically the robot has a large working area which can be hazardous (for example, it can hit the patient and/or surgeon if a large move is commanded by accident). Therefore the size of the robot's workspace has to be constrained by some safe means (typically by mechanical means).        
The needs highlighted above are mostly for brachytherapy systems, but there are other medical instruments which require precise positioning and orientation. For example the proper positioning of a high-power laser source used for the treatment of enlarged prostate in a procedure termed benign prostate hyperplasia (BPH) is also needed.